User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

Set up a fresh Thunderbird Beta 78, filled Account settings (same as in 68 - wich are working), tried the same with the updates up to 79.01b

Actual results:

Thunderbird does not fetch mail and does not show an error, but in error console:
[Exception... "Component returned failure code: 0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH) [nsIXPCComponents_Utils.readUTF8URI]" nsresult: "0x80520001 (NS_ERROR_FILE_UNRECOGNIZED_PATH)" location: "JS frame :: resource://gre/modules/L10nRegistry.jsm :: L10nRegistry.loadSync :: line 684" data: no] L10nRegistry.jsm:684:19
loadSync resource://gre/modules/L10nRegistry.jsm:684
fetchFile resource://gre/modules/L10nRegistry.jsm:599
generateResourceSetSync resource://gre/modules/L10nRegistry.jsm:504
map self-hosted:231
generateResourceSetSync resource://gre/modules/L10nRegistry.jsm:499
generateResourceSetsForLocaleSync resource://gre/modules/L10nRegistry.jsm:441
next self-hosted:1190
generateBundlesSync resource://gre/modules/L10nRegistry.jsm:178
next self-hosted:1190
touchNext resource://gre/modules/Localization.jsm:167
generateBundles resource://gre/modules/Localization.jsm:473
<anonymous> chrome://openpgp/content/modules/trust.jsm:11
<anonymous> chrome://openpgp/content/modules/keyRing.jsm:17
<anonymous> chrome://openpgp/content/modules/windows.jsm:19
loader chrome://openpgp/content/modules/lazy.jsm:20
getService chrome://openpgp/content/modules/core.jsm:453
getService chrome://openpgp/content/modules/core.jsm:210
init chrome://openpgp/content/BondOpenPGP.jsm:78
<anonymous> chrome://openpgp/content/BondOpenPGP.jsm:97

Its the same as i reported in bug 1634341, but this was about Version 76. I am not sure if i should have been setting up this bug extra because it's 79.01b

Same problem here.
I've tried both upgrading from an old, functioning TB 68 profile and adding a new mail account to a clean new TB 78 profile, same result.
TB shows "Checking mail server capabilities" and that's it.

No need for the dupe. We track all versions in the same bug.
(I think that error is "harmless" and not the cause of other problems.)