I've been using a combination of bluehost.com with phpgallery for private photos plus iCloud Photo sharing, but there are two problems:
- Bluehost.com shared hosting is just unbearably slow for this purpose, not surprising given the low fee, even with unlimited storage it takes a long time to load and managing the gallery is definitely a pain.
- iCloud works pretty well for iOS users, but not at all for Android. Also, with sharing, they limit the resolution of the photos to 2Kx2K which isn't so nice with 50MP images, so you don't get high resolution. You can pay more, but they are pretty expensive.
There are a couple of options that are marginal cost zero if you already have Amazon Prime or use Google Gsuite to manage your mail for you anyway because Spam stinks. Both allow unlimited photo storage at unlimited resolutions (if you pay for Google Drive unlimited at $10/month).
The main issues are:
Amazon Prime Photos. This is great and free and allows unlimited storage. The main gotcha is that you lose control of the naming of the photos. This makes it pretty useless if you've got say 40K photos across five families (hint!). It basically names it all to Date.jpg
Google Photos. This is a pretty chimera, you basically have a separate uploader that only works against non-network drives for Mac and Windows. There is a buried checkbox that says, when you are uploading photos, do you also want them to go into Google Photos. There is also another buried option in Google Drive which says do you want to see your Google Photos inside Google Drive. If you do this, then you can download.
The other interesting oddity if that if your photos are less than 2MP and videos are 1080P then it doesn't count against your Google Drive quota.
Synology does have a Cloud Connect feature so you can in the background dump all your files onto Google Drive. This is not the same as Hyper Backup which does the same but at the block level for storage. However, if you can't use Cloud Connect to upload Google Photos.
So if you have photos say on a network server, the only way to do this is to download your photos to your laptop so it isn't a network drive and then upload it with the batch uploader with the Google Photos option checked.
Net, net, the best way so far seems to be to use Google Drive to host all the photos using the $10/month unlimited GSuite plan and then selective add those photos to Google Photos for album sharing.
I haven't gone through the whole process yet, but it does look like you do lose all the directory and file names like Amazon Photos. So there isn't an answer quite yet. I may in the end have to host my own Digital Ocean site with a custom gallery 🙁