Icedove 68.8.0 cannot get add-ons on Trisquel 8

Trying to install add-ons on Icedove:
1. Open Icedove.
2. Open the Add-on Manager by pressing F10 to make the Menu bar visible, then deploying the Tools menu, then clicking on the Add-ons item.
3. Introduce the name of the extension on the field "Search for more extensions", then press Enter.

The results show that the entire add-on installation is misdirected to Abrowser:
-A new tab in Icedove is open, showing a web page corresponding to the search, whose address is "https://trisquel.info/en/browser-plain?keys=" and then the search term. Notice the "browser" in the address. On an unrelated note, this web page can be displayed all the same in a browser, just by copying the address and pasting it at the browsers address bar.
-The add-ons search results are always related to ABROWSER, never to ICEDOVE - Greasemonkey will appear, Enigmail or Lightning will not.
-Clicking on the name of one extension appearing in the results will open the extension web page, this time in the browser rather than in an Icedove tab. This web page, with an address beginning with "https://trisquel.info/en/browser/addons/", offers a link for "Install extension", but not for downloading it. Again, notice the "browser" in the address.
-Clicking on the "Install extension" link causes the extension to be installed in ABROWSER, not ICEDOVE!
-Right-clicking the "Install extension" link allows for downloading the .xpi file, which can then be tried to install from the Add-on Manager by clicking on the gear icon, clicking on the Menu item "Install add-on from a file..." and then selecting the file. However I cannot attest that this works as intended because so far all of the add-ons that I downloaded were rejected because of incompatibility with Icedove 68.8.0. Really, I cannot find an Add-On that works right with Icedove 68.8.0, other than the three that come installed with it.
-Fix: I guess that I should try to download and install the add-ons from the Thunderbird store then.