When travelling (for work or for leisure) I always have my Chromecast Ultra dongle with me.
I just hook it up to the hotel tv HDMI and it connects to a wifi hotspot on my phone.
That way I used Plex for years without an issue.
On the new experience app that’s not possible anymore, because the App just doesn’t let me cast (“please enable wifi to cast”).
I would be very glad if that could be fixed.