Currently it supports only TOTP because that's what most services seem to use.
The app utilises -
OTP.Net for TOTP generation https://github.com/kspearrin/Otp.NET
ZXing.Net for reading QR codes https://github.com/micjahn/ZXing.Net
QRCoder for creating QR codes https://github.com/codebude/QRCoder
Google protobuf for reading Google QR code protobuf message https://github.com/protocolbuffers/protobuf
Utilising .proto file from https://github.com/scito/extract_otp_secrets