Apache OpenOffice

Cryptee

CryptPad

Etherpad

LibreOffice

Mailfence Documents

OnlyOffice

Proton Docs (an end-to-end encrypted, collaborative document editor found in Proton Drive powered by Proton who also have SimpleLogin, Protonmail, Protonmail Bridge, ProtonVPN, Proton Pass, and Proton Calendar.)

Rocket Tech Docs (Christian, conservative company)

Rocket Tech Spreadsheets (Christian, conservative company)

Zoho Docs