

I’m not familiar with the reddit filtering but have you tried using cloudflare page rules? You can try capturing everything after the .tld and then forward it to a lemmy server. So for instance somedomain.tld/12345 could forward to lemmy.world/post/12345. If reddit is checking links for 301 redirects to lemmy though then that wouldn’t work.
A more advanced approach would be to use a cloudflare worker to do a proxy response so the status code is returned as 200 OK instead of 301 redirect. I haven’t tried that but i think that would be much harder for them to block and you could always make more elaborate urls to make it harder to find obvious lemmy-like structure
Without knowing what reddit is doing, I’m not sure. A JS redirect could be detected, but if OPs paid shortener service is working then reddit is probably working off a simple domain block list. In that case you could use throw away domains.
But JS redirect, proxy response, etc all could just become a game of cat and mouse. Just depends how motivated either side is. But given how big reddit is, i think you’d have the advantage at least in the beginning. Just gets expensive since each time your domain gets blocked you’ll be paying to register a new one.