AMD drivers: use the built-in MESA drivers that include the official AMD support.
Gmail: ProtonMail for the service, Kmail for the desktop client.
Chrome: Firefox, or Librewolf if you care about privacy.
Office365: LibreOffice for full FOSS or OnlyOfficr for less freedom but more comfort.
iTunes: depends entirely on what you use it for, but I buy my music mostly off of BandCamp these days.
MuseScore: MuseScore
Norton: Why were you using Norton in the first place? It's practically a virus itself. If you need an antivirus on Linux, you might want ClamAV/ClamTK for something that runs locally only, or Microsoft Defender for Linux.
Py-Charm: Py-Charm, VSCode, Vim, Kate/KWrite
Remote Desktop to iOS: I got nothin'
Star Citizen: Star Citizen
Steam: Steam
VPN: Wireguard
Windows Games: install locally using Wine and then add to Steam as a non-Steam game to use Proton for better support.
Windows 10: run it in a VM if you still need it, or keep it on a separate SSD and dual boot into that.