Well currently uploading some files, so I thought it would be great to revive this forum a bit while doing so

I highly recommend to take a look at Affinity Photos Equirectangular Projection method
https://affinity.serif.com/en-gb/photo/Unlike Photoshop wich produces those black triangles on top and bottom after doing some panosphere painting and unwrapping it back, Affinity produces a smooth transition at the nadir point. (and yes it supports floating point exr)
The downside is, that Afinity does not have such a good memory management like photoshop has, so you need more physical ram to work on large scale panoramas.