It looks like v0.19.0 support will keep photon compatible with v0.18.0. I just need to send both query parameter and a header, so that v0.19.0 will accept the header and v0.18.0 will accept the parameter. I thought v0.19.0 would deny the query parameter, returning an error. Thankfully, the Lemmy devs were sane.
I'm still working on it. It's not too difficult, I've actually finished compatibility, but I'm implementing the new features to maintain my claim of feature parity.
Good to know it's not very intensive. Also amazing client you have made. The UI is so clean and good it's obvious that somebody with great experience in UI design has made it