Can't install addon even after removing install.rdf and adding manifest.json

I’m trying to install extension to Thunderbird (version 68) from here . It’s an extension of old type - overlay extension, and this type of extension is not supported anymore. I unzipped it, replaced install.rdf with manifest.json with such content:
“manifest_version”: 2,
“applications”: {
“gecko”: {
“id”: “mexint@karel.gudera”,
“strict_min_version”: “68.0”
“name”: “MExInt”,
“creator”: “Karel Gudera”,
“version”: “2.0”,
“legacy”: {
“type”: “xul”,
archived all (with zip algorithm, but xpi extension), and tried to install to Thunderbird. It seems to me that I’ve done everything according to this instruction, but it doesn’t work, Thunderbird says “this add-on could not be installed because it is not compatible with Thunderbird 68.8.0”. What have I done wrong?

When you get that message it’s often just the format of the JSON file. Look at the browser console (somewhere in developer tools) and you’ll see an error message:
Invalid XPI: SyntaxError: JSON.parse: bad control character in string literal at line 2 column 3…
The problem is that you have ‘smartquotes’ - “manifest_version” instead of ordinary double quotes - “manifest_version”:
Use a text editor, not a word processor.

“type”: xul, shouldn’t have a comma on the end. A very common problem - look for that first!

Correcting those two I still got warnings. I compared it with a converted addon of mine and replaced the legacy key with “legacy”: true

That got rid of the errors and warnings. But it won’t install on this Linux system (TB 68.8). (I used the Linux version of the addon, obvuiously.) That doesn’t surprise me - it’s not a simple addon and I’m sure there are more changes required than just the manifest. But you could try it on 68.0 on Windows.

The problem was in comma after “type”: xul, thanks. It works at first glance, but hangs during addnig Microsoft Exchange Account. Yes, obviously, there are more changes required then just the manifest. Thanks anyway!