Find

# find Syncthing conflicts
find ~ -name "*.sync-conflict-*"
# delete files with modification date older than specified date
find . \! -newermt "2020-01-01" -delete

find . \! -name "something"
# or:
find . -not -name "something"

fdfind is an alternative to the default find tool. It's faster and more user friendly.

Package name: fd-find (Fedora)