From ghacks (comment section): https://www.ghacks.net/2019/05/04/your-firefox-extensions-ar...

This should allow the extensions to work until the next check (Verified locally):

1) Shut down Firefox

2) Open extensions.json (located by about:profile -> Root Directory)

3) Replace all instances of “appDisabled”:false to “appDisabled”:true

4) Replace all instances of “signedState”:-1 to “signedState”:2

5) Save and close extensions.json

6) Start Firefox

7) Close Firefox

8) Open extensions.json

9) Replace all instances of “appDisabled”:true to “appDisabled”:false

10) Start Firefox

11) Disable and re-enable all extensions in about:addons