[BUG] Valid feeds resulting in "This feed has encountered a problem"

**Describe the bug**
The following feeds are listed as having errors, but validate according to validator.w3.org (couple with minor errors, but jlist is completely valid), and all are accepted by other applications without complaint (e.g. Feedly).
https://jlist.com/blog/feed/
https://blog.cloudflare.com/rss/
https://www.scottberkun.com/feed/

The error is (rather misleadingly):
> Blast! This feed has encountered a problem. Please verify that it is always reachable then update it.
Hard to say what the real issue is, as the error above is all I get, and is plainly wrong.

**To Reproduce**
Steps to reproduce the behavior:
Subscribe to the above sites in FreshRSS

**Expected behavior**
I should get a list of articles from the feed.

**Environment information (please complete the following information):**
- Docker image: lscr.io/linuxserver/freshrss
- Device: Irrelevant
- OS: Irrelevant
- Browser: Irrelevant
- FreshRSS version: 1.19.2
- Database version: Unknown; image does not indicate and FreshRSS UI also does not indicate
- PHP version: 7.4.26
- Installation type: Docker

Installation check
PHP installation
Your PHP version (7.4.26) is compatible with FreshRSS.
You have the cURL library.
You have PDO and at least one of the supported drivers (pdo_mysql, pdo_sqlite, pdo_pgsql).
You have the required library for regular expressions (PCRE).
You have the required library for character type checking (ctype).
You have the fileinfo library.
You have the required library to browse the DOM.
You have the JSON extension.
You have the recommended mbstring library for Unicode.
You have the ZIP extension.

File installation
Permissions on the data directory are good.
Permissions on the cache directory are good.
Permissions on the users directory are good.
Permissions on the favicons directory are good.
Permissions on the tokens directory are good.

**Additional context**
Wish I could give you some, but FreshRSS doesn't have any useful error messages.