Riecoin Core 22.03, based on Bitcoin Core 22.0, was recently released, but Gapcoin is still yet at 0.16.3 and not sure that SegWit is even activated... Let alone TapRoot/Schnorr Signatures.
No, segwit is not enabled for the Gapcoin chain, there's a handful of inveterate 0.9 holdouts -
https://chainz.cryptoid.info/gap/#!network and we've been disinclined to force the issue (the Riecoin community seems rather more coherent). However, I take your point about the disproportionate negative impact of unnecessarily-duplicated effort. There is one unfortunate difference in the mining aspect, the "unreconstructed" GapMiner code still depends on the
getwork RPC-API call and so that has to be re-implemented for each Gapcoin upgrade.
AIUI, 0.16 is the last Bitcoin version that enables versionbit "soft fork" upgrades, after 0.16 the segwit starting block height is hard-coded and (again AIUI) migrating to a more recent version would entail a hardfork - so that's why Gapcoin is frozen at 0.16. I did get an 0.20 version working but didn't take it to production. However, looking through the Riecoin release history it appears you folks successfully managed a hard fork from 16 to 20, which is encouraging.
I have some ideas that I'm working on with respect to mapping the blockchain into RDF (e.g.
https://github.com/gapcoin-project/gapcoin-core/blob/6828bdebf2f07367799e41b04e081de24e322057/src/rpc/blockchain.cpp#L2186) and I'm doing some groundwork atm.
Cheers,
Graham