For both OP Nigel and
@Jellycat (though not for Wi-Fi which I never considered):
Before I got a bluetooth-equipped integrated amp, I had an original Cyrus One amp running my main stereo, and a Nakamichi SoundSpace 8 as a secondary one. Neither of these great devices had Bluetooth and I also wanted to connect my phones and a Surface Pro to stream both Spotify Premium, which I had at the time, and my digital file collection. (I had also inquired about modifying/"bluetoothing" my systems and could not.)
What I got was this little solution X 2:
https://www.amazon.com/Bluetooth-Adapter-Streaming-Wireless-Speakers/dp/B016NUTG5K/ref=sr_1_8?crid=E3LASN8O7AHB&dib=eyJ2IjoiMSJ9.zphMgdfoIjRbdIgExwgpjnEXook_xhQsl1ehxP5KX_uSmC2x4Manw60C5twL-BKlWv-B7GP-pcPFTotLKT4XFW7-AdXGwgcZXRxe5m-BHYcfvrSXiv9duYaClzQEiqH4cxpKhWgIkYRRH67PgdmCdvBZ8siRw82mcn5LzP8-PfiJ2vbzAg8qDwJhDwebnz45lmqkk8l7CD8kQhvteUfw1KK51ytVPI3aR4VEN0kx3bc.COwPmANfAsuzDRX7Llxg9eMaGoi8E8g2w-TZMAoZ0X8&dib_tag=se&keywords=bluetooth+adapter&qid=1716143709&sprefix=bluetooth+adapter,aps,113&sr=8-8
If you have an open auxiliary input on your Denons, try this. I found it to be a very economical and reliable solution for both of my systems for a few years. The Esenkin can also connect via an audio jack, but yous probably wouldn't like having this adaptor dangling from the front of your nice compact Denons.
Not sure how available this is around the globe, and there there may may be better adaptors in 2024; but I do see plenty of current satisfied reviewers as I did several years ago when I got my units. I still have the Esenkin adapter connected on the back of the Nak, but I rarely use a bluetooth connection on it these days.
Note, this does not Bluetooth the Denon: it is only an adaptor and it may or may not be enough for you. I found it to be a convenient quick adaptation of my otherwise-worthy devices, and you can see at amazzon dot com that they have sold many thousands of these devices over a bunch of years. Good luck enabling your Denons and your phones.