Cannot subscribe to a valid RSS feed: "Invalid subscription"

Platform

Desktop - Web

Describe the bug

W3 feed validator says the RSS feed https://www.404media.co/rss is a valid feed.

But Folo reports errors when I try to subscribe to it.

13-B4t1nNu9.js:5 Error: Invalid subscription
    at mu (main-_yevSFOE.js:33:131483)
    at main-_yevSFOE.js:34:7929
    at main-_yevSFOE.js:33:8766
    at Rt.produce (2-Dom3MH6f.js:1:6715)
    at main-_yevSFOE.js:33:8746
    at r [as setState] (2-Dom3MH6f.js:17:980)
    at main-_yevSFOE.js:33:8734
    at hN.upsertManyInSession (main-_yevSFOE.js:34:7896)
    at CR.optimisticExecutor (main-_yevSFOE.js:34:8341)
    at CR.run (main-_yevSFOE.js:33:9195)
    at hN.upsertMany (main-_yevSFOE.js:34:8441)
    at pN.subscribe (main-_yevSFOE.js:34:10378)

main-_yevSFOE.js:33 Uncaught (in promise) Error: Invalid subscription
    at mu (main-_yevSFOE.js:33:131483)
    at main-_yevSFOE.js:34:7929
    at main-_yevSFOE.js:33:8766
    at Rt.produce (2-Dom3MH6f.js:1:6715)
    at main-_yevSFOE.js:33:8746
    at r [as setState] (2-Dom3MH6f.js:17:980)
    at main-_yevSFOE.js:33:8734
    at hN.upsertManyInSession (main-_yevSFOE.js:34:7896)
    at CR.optimisticExecutor (main-_yevSFOE.js:34:8341)
    at CR.run (main-_yevSFOE.js:33:9195)
    at hN.upsertMany (main-_yevSFOE.js:34:8441)
    at pN.subscribe (main-_yevSFOE.js:34:10378)

Entry ID

No response

Relevant Information

No response

Reproduction Video

No response

Environment

No response

Validations

• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A, please open a GitHub Discussion instead.
• This issue is valid

Contributions

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests (actually just go ahead and do it, thanks!)

Start by reproducing the subscription attempt for https://www.404media.co/rss and inspect the reported pN.subscribe, hN.upsertMany, and mu entry points in the bundled files. Done means this validator-marked valid RSS feed can be subscribed to without the “Invalid subscription” error.