For anyone having those problems, here's quick update for this one: After a few weeks someone from the Postiz Discord (terrible way and platform for bug reporting btw) suggested to set up Cloudflare R2. It took two restarts, but after that I managed to connect my LinkedIn pages, because apparently it wasn't able to store the profile images and thus created that redirect above.
Although, now that I'm writing this, the bucket it still empty, but there are files in /app/data/data/2025/11/27 (the second data folder wasn't there yet, I needed to create that one manually, maybe that solved it after all?)
Also, even with the working connection, this error appeared in the logs, maybe we could let that point to somewhere it can write:
Nov 27 19:37:40 ⨯ Failed to write image to cache x5s7nobKRgx-CJ5Nq4z9X1PXnOjxJPxqtCDckv+9gKk= Error: ENOENT: no such file or directory, mkdir '/app/code/apps/frontend/.next/cache/images'
Nov 27 19:37:40 at async Object.mkdir (node:internal/fs/promises:860:10)
Nov 27 19:37:40 at async writeToCacheDir (/app/code/node_modules/next/dist/server/image-optimizer.js:190:5)
Nov 27 19:37:40 at async ImageOptimizerCache.set (/app/code/node_modules/next/dist/server/image-optimizer.js:574:13)
Nov 27 19:37:40 at async /app/code/node_modules/next/dist/server/response-cache/index.js:121:25
Nov 27 19:37:40 at async /app/code/node_modules/next/dist/lib/batcher.js:45:32 {
Nov 27 19:37:40 errno: -2,
Nov 27 19:37:40 code: 'ENOENT',
Nov 27 19:37:40 syscall: 'mkdir',
Nov 27 19:37:40 path: '/app/code/apps/frontend/.next/cache/images'
Nov 27 19:37:40 }