Raspberry Pi phone

Are there any reviews/comparisions on Phone (GSM, 4G,LTE)boards/Hats for the Raspberry Pi?
I see a lot now advertised but no real reviews or comparisions.
I’m looking to do 2 things. Make my Pi3B+ mobile. And make a Phone, hopefully with the PiZero W.
Has anyone done any projects? I’m looking for input for which is the best board (with user support/manual/instructions etc).

Quick google

https://www.raspberrypi.org/blog/piphone-home-made-raspberry-pi-smartphone/
https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone
https://www.raspberrypi.org/blog/tytelli-a-diy-smartphone/

Not sure on the different modules, but I do know many are making custom interface boards

Everybody thanks for the responses. I’m aware of all (or most) of the projects and boards.
What I was looking for is side by side reviews of the products so I don’t have to read a ton of
material and purchase the best board(s)/solutions for my use.
I was really wondering if anyone would answer who had done any projects and have any idea which is the best.

I don’t want the one with the board with the buttons on it. I want to use a touch screen and write my own apps in Python.
The ones I’ve come accross are.

https://sixfab.com/product/gsmgprs-shield/?gclid=CjwKCAjwns_bBRBCEiwA7AVGHjxYNZZx0204LkJev4pGSNOZRsv6Hr3kX6aeasxaX-ztka1p0IXxuhoC7pUQAvD_BwE
https://randomnerdtutorials.com/sim900-gsm-gprs-shield-arduino/
https://www.waveshare.com/wiki/GSM/GPRS/GNSS_HAT
https://www.newegg.com/Product/Product.aspx?Item=9SIABKS5R53595&ignorebbr=1&nm_mc=KNC-GoogleMKP-PC&cm_mmc=KNC-GoogleMKP-PC--pla--Gadgets-_-9SIABKS5R53595&gclid=CjwKCAjwns_bBRBCEiwA7AVGHpExg4_LDnIq_rGL7_iVFe06nCS2XSInXUzH_r0-jsCvWlGh79Kx1hoCfFUQAvD_BwE&gclsrc=aw.ds
https://www.itead.cc/raspberry-pi-sim900-gsm-gprs-add-on-v1-0.html
https://www.pianywhere.com/

The SIM900 (randomnerdtutorials) seems to be the standard for the industry and was used in the Pi Phone. The Pianywhere has multiple versions.
There is a ton of info on setting these up. I’d just like to know if there are any reviews/comparisons for these boards before I continue.

I’ve recently read an article not to use SIM900 and SIM800 series in the USA since 2G is phasing out.
The alternative is the more expensive SIM7100E! What are your thoughts on the issue?