So I am gray ace, leaning heavy on the dark gray side of things. I am also AFAB, aromantic, polyamorous, kinky and sex-favorable. My experiences are my own and I am sharing though this lens. I discovered I was asexual while in two different romantic-sexual relationships. This revelation impacted each of these connections in different ways. In every relationship since, my asexuality seems to have a different effect.
This is my own experience of asexuality in the various ace/allo connections I have had over the years. As with everything, your experience might be different and millage may vary.
Personally I have found in hugely beneficial to get creative with how to incorporate non-sexual intimacy in relationships. For me it can take the form of kink/BDSM, showers/baths, non-sexual nudity, cuddling, caretaking, service/acts of love and quality time. Figuring out what worked in different relationships took time and exploration. It meant asking "what makes you feel close? wanted? vulnerable? safe? loved?" and brainstorming activities that were comfortable for both of us, and identifying and engaging in the ones that met the emotional needs that sex can fill for my allosexual partners.
In some of my relationships I have been sexually active and in others we are not. In all cases, a willingness to validate, listen and understand my partners experience as allosexual was just as critical as their willingness to do the same towards my asexuality. For some relationships I have been in, sex, or rather lack there of, was a deal breaker for that person. For others, no sex was comfortable and something they were okay with. It has varied connection to connection.
I have found that when I am able to hear (listen, validate and seek understanding) my partners talk about how a lack of sex is affecting them - physically, mentally and emotionally - they feel more supported by me, and are more comfortable and able to be more understanding of my own counter perspective. This doesn't mean tolerating guilt-tripping or coercion - but rather giving them the space to express how their experience is different than mine, where they are struggling, what they are feeling, and validating that experience without asking for change. Blue balls/ovaries are a thing, and masturbation can help relieve that sensation - but masturbation does not meet the sexual needs for everyone and in every case. Understanding that this is not a viable compromise for everyone has been important in the discussions I have had with partners. Even in the relationships I have had where there is no sex, being able to listen to complaints/expressions of how the lack of sex is affecting them (physically, mentally and emotionally) is important to my own understanding of how sex and sexuality plays a role for them as an individual.
Just as with intimacy, creativity has helped the dyads I have been in find compromises that both parties can be happy with. Sometimes it has looked like sex whenever the other person wants to. Sometimes this has looked like sex-schedules, or certain regularity. Sometimes this has looked like sexting, or talking to them while they masturbate - or even having them masturbate to me or with me, without my own involvement, just my company. Sometimes this has looked like group sex, where I talk, kiss and watch but do not participate in directly sexual ways. Sometimes it has looked like non-sexual BDSM. Sometimes it means no-sexual contact at all. I have found success in being willing to have the conversations about what works and what doesn't, having the conversation beyond "sex or no sex" and talking more about "what activities meet what needs? what activities meet similar needs? can those activities look different? can those needs be met in a different way?" etc etc etc
Where my own comfort is with sexual contact has changed over time (in both directions) and within relationships, and relationship-to-relationship. For me, knowing I can always talk to my partner when my desires/willingness has changed is critical. Knowing that the willingness to have the (sometimes quite hard) conversation makes me feel safe - knowing we can talk about what we want/need and how that change may change what is on the table in our relationship. And same for them - I want and encourage my partners to talk to me when they feel that way too. Historically, keeping this avenue of communication open has helped prevent resentment from building in my relationships.
I have been polyamorous in all of my relationships, however I have learned that being in an open relationship is not a catch-all solution for the ace/allo conflicts that can occur in the relationships I have been in. Yes - sex can be had elsewhere, yet sex elsewhere often does not meet the emotional need my partner has for sex within our relationship. Personally, I find that knowing that sex can be had elsewhere does relieve personal stress I feel around wanting that need met for my partner. For me, it takes the pressure off.
Furthermore, some people do not want other people, or sex outside the relationship, or 'meaningless' sex, or sex without love. I have found that telling my partners to meet their own needs elsewhere, has lead to them feeling dismissed, misunderstood, and disconnected from me - even when meeting needs elsewhere is the solution we ultimately utilize! I have found more success in keeping the discussions about needs within a relationship, to that relationship.