We use a self-hosted version of Next.js with the standalone output and don't experience any limitations with using ISR.

Regarding other aspects, I suggest looking into OpenNext. They focus on decoupling existing features from Vercel's vendor lock-in and provide instructions on deploying Next.js on AWS/Cloudflare independently. However, I haven't looked into the limitations in detail, and you should keep in mind that they might not support all Next.js features, considering the frequent releases.