Hello! Following worked for me:
Download and install one by one the packages gcc-10-base and libgcc-s1, after that upgrade to Opera 88 works.
http://ftp.de.debian.org/debian/pool/main/g/gcc-10/gcc-10-base_10.2.1-6_amd64.deb
http://ftp.de.debian.org/debian/pool/main/g/gcc-10/libgcc-s1_10.2.1-6_amd64.deb