Balance between native speakers of any language and speakers of other languages interested to learn this language is ... very unbalanced :-)
For an English L1 speaker learning most other languages, there are more L2 speakers trying to learn English than vice versa. And likely these few L2 speakers are learning English.
If not (as OP mentioned in comments, Irish (or Welsh) native speakers are likely fluent in English): consider looking through language exchanges to find out which language are native speakers of your target language trying to learn most often. For Irish, it might be Spanish. If so, becoming reasonable proficient in Spanish (enough to be interesting exchange partner) will give you a chance to trade Spanish (your L3) for Irish.
Also, on many forums (with some efforts) you can find few people who want to help others to learn their native language without exchange to other language (often retired teachers). I would assume it would be especially a case for languages which are trying to be revived, like Irish or Welsh.
Another trick: On language exchanges with freemium business model (free = non-paying members have limited abilities to contact other members): if you cannot decide if it is worth to become paying member - send just a free message. If you get a response (even if it is a free message back), you can see you have a potential partner, and decide to buy shortest/cheapest membership available.
When you become paying member (with abilities to contact others), do active research and message many potential partners (who look interesting: they put some effort to create a profile), and send them your contact email outside the exchange. So even if they get your message weeks later (when your short-time membership expired), they can contact you outside of the exchange.
Most people create the profile but do not put the effort to contact other people, so if you actively contact others, you will have a competitive advantage. Having a picture and a carefully written profile gives you extra edge. Changing your picture every few months gives you more: a person who skipped over last time might give you another chance.
Be considerate what you write in the initial contact: if you spend any time on freemium exchange sites, you will learn that many such contact are from scammers, looking for romance, so initial contact should demonstrate you have serious interest to learn and help your partner to learn.