Convert deb to eopkg?

No tools are provided for doing that.

There is no magic, push a button program.

Learn to package for Solus, then you can use existing examples where Solus repackages .deb's as a guide. (Solus only does this when it can not be built from source)

Some examples include:
opera-stable vivaldi-stable vivaldi-snapshot brave

You need to have some idea of what you're trying to achieve and then use those examples as a guide, its a package by package basis. Not just copy & paste and have everything work nor is it as simple as extracting the .deb to / which can break things when files get overwritten etc and can not be tracked by the package manager for later removal.

nihi1ist
Well it has been abandoned for 3 years. I wouldn't trust it.

Its also noted by ikey that it was never intended to be universal either.
https://github.com/solus-cold-storage/fpi/issues/1#issuecomment-336727032

So assuming it ever worked / still does. Your results may vary.

Likely not going to work, was never completed nor is it supported by us, hence why it's in cold storage.