[Technology] Telephone advice needed for digital hearing aid user

Hope some tech whizz can help please.
My 88yo mum wears digital hearing aids and struggles to hear the voice on a landline (even with a special phone that boosts sound to 50dB).

She can hear OK when I Skype her as they're bluetooth connected to her ipad, but as she has dementia she struggles to use devices like that and mobiles.

Mobile reception there is rubbish so I can't rely on the call getting through even if she had a phone that could be paired with her hearing aids.

I've been looking for a landline phone with Bluetooth technology but they don't seem to exist.

I know that phones are increasingly connected to the Internet not copper wires but this still doesn't appear to offer a solution.

Any tips please? Ta.

my neighbour is deaf as a post and he struggles with this big time.

Thankfully, I do not have these issues (yet!) - but have you looked at these sites? They seem to offer decent advice / suggestions - https://rnid.org.uk/information-and-support/technology-and-products/using-your-landline-phone/ and https://www.healthyhearing.com/help/assistive-listening-devices/hearing-aid-compatible-phones or https://www.hearinglink.org/technology/telephones/ (more detailed explanation of the technologies involved).
Good luck!

You might be able to ask for a hearing loop which works with a phone etc.

There are a number of devices the hard of hearing and deaf people can claim, like a vibrating smoke alarm, alarm clock and flashing light for the doorbell.

https://www.nidcd.nih.gov/health/assistive-devices-people-hearing-voice-speech-or-language-disorders