Good point, if supporting JS disabled browsing is a goal, SSR is a must.
re languages If doing SSR, language matters. If doing CSR, statically generating site, it matters less. For example, there are more hosting options for PHP than Rust. There are even more hosting options for static assets (eg CDN).
I’ve always seen these self hosted S3 API compatible services as something a developer would use for testing.
Could maybe simplify the solution with https://syncthing.net/ or https://restic.net/ for self hosted backups.