Ubuntu升级至22.04后仅第三方PPA更新失败的问题求助

大家好，我碰到一个挺奇怪的问题，想请各位帮忙分析下：

我的机器原本是Ubuntu 18.04 LTS，先升级到20.04，再升级到了22.04，机器处于代理环境下（我已经正确配置了代理）。目前从Ubuntu官方仓库更新、升级软件都没问题，所以我觉得网络配置应该是正常的，但所有非官方PPA的更新都会报错，具体情况如下：

执行命令 sudo apt update 后，得到的输出是：

Ign:1 https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu jammy InRelease
Ign:2 https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/Ubuntu_22.04  InRelease
Hit:3 http://archive.ubuntu.com/ubuntu jammy InRelease
Hit:4 http://archive.ubuntu.com/ubuntu jammy-updates InRelease
Get:5 http://archive.ubuntu.com/ubuntu jammy-backports InRelease [109 kB]
Hit:6 http://archive.ubuntu.com/ubuntu jammy-security InRelease
Hit:7 http://dl.google.com/linux/chrome/deb stable InRelease
Ign:1 https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu jammy InRelease
Ign:2 https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/Ubuntu_22.04  InRelease
Ign:1 https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu jammy InRelease
Ign:2 https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/Ubuntu_22.04  InRelease
Err:1 https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu jammy InRelease
Could not handshake: An unexpected TLS packet was received. [IP: 134.226.56.7 8080]
Err:2 https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/Ubuntu_22.04  InRelease
Could not handshake: An unexpected TLS packet was received. [IP: 134.226.56.7 8080]
Fetched 109 kB in 7s (15.3 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
3 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: Failed to fetch https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu/dists/jammy/InRelease  Could not handshake: An unexpected TLS packet was received. [IP: 134.226.56.7 8080]
W: Failed to fetch https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/Ubuntu_22.04/InRelease  Could not handshake: An unexpected TLS packet was received. [IP: 134.226.56.7 8080]
W: Some index files failed to download. They have been ignored, or old ones used instead.

从报错信息来看，这像是个网络问题，但为什么只有非官方PPA会出现这种情况呢？有没有大佬能给点解决建议？

备注：内容来源于stack exchange，提问作者Erwan