My reasoning for suggesting unlisted instead of private is because the recipients might not have a YouTube account, so making it unlisted means they’re certainly able to view the video.

Have you considered keeping them on YouTube but unlisted, so that they don’t show up on your profile nor in youtube searches?

Otherwise, you could create a Google Photos album, but either quality suffers, or the videos will take a lot of space.

All the other options I could suggest either call for a recurrent payment, but trust me, it gets tedious after a while (ie. VPS with Peertube or similar), or call for losing quality by a lot (ie. Whatsapp or Telegram channels/groups), or quickly become unpractical (ie. Mega, Dropbox…)

There are plenty of choices, and if you’re 100% sure you’re fine with recurring payments and having to constantly mantain a system/keep it updated and secure, then go ahead and make a VPS, but if you’d rather have it be convenient, look into additional YouTube settings or common alternatives like Vimeo.

Have you looked into Cloudflare Tunnel? It’s a turnkey solution that does exactly what you want. No idea what the cost is though.