Unable to boot without nomodeset - complete freeze

Already have played with Ubuntu on older spec desktops with no issues at all, however when when installing Ubuntu 18.04 from installation USB on this machine, had to boot with nomodeset to overcome freezing as a result of Ubuntu 18.04 not recognising/supporting these drivers

After install, this machine will not boot up at all without nomodeset

When trying to boot without no modeset, it seems to be the Radeon Driver which causes boot sequence to got into a tizz

Video handling resorts to llvmpipe (LLVM 9.0.0, 256 bits)

My problem is that Video Playback VLC very choppy - seems to get a little better when minimised, but effectively not usable.

Have tried many threads posted regarding this problem, but nothing seems to work.

Would really like to migrate my workload onto Ubuntu 18.04 operating system, but this seems to be a real non starter where i can't play video content, as video editing is a core function in my workload.

Not sure if there is a solution for this, however after researching many similar threads, coupled with your in depth response to similar problems leaves me hopeful that you can point me in the right direction, or worst case scenario tell me there is no solution at all, and that I will have to stick to the hateful Windows 10 which is supported and working.

1) not sure if it is just a simple graphics acceleration problem ?
2) as flgrx no longer supported (for AMD Catalyst on Radeon HD 6470 M - can I disable this GPU somewhere on boot - as this seems to be where boot goes into a tizz. If so, how would I do this.
3) if i did this would XORG then recognise other GPU - Intel HD 3000 and give me correct rendering to eliminate choppy video

I am a noob, but have been playing with Ubuntu for some time, albeit at very low level, not totally computer illiterate, but do feel I am out of my depth in trying to resolve this. It just seems odd that it works fine on much lower spec and older desktops, but that I cant get this to work on my not so outdated laptop.

Ubuntu Release 18.04.3

Also seems akin to Bug #1784473 recently reported

Same for me, I am not able to use Xubuntu without "nomodeset" in grub. Usualy after login to XFCE is is freezed and I have to power off my notebook by holding of power button.

My configuration:

System: Host: tomas-ntb Kernel: 5.3.8-050308-generic x86_64 bits: 64 Desktop: Xfce 4.12.3
           Distro: Ubuntu 18.04.3 LTS
Machine: Device: laptop System: HP product: HP EliteBook 745 G5 serial: N/A
           Mobo: HP model: 83D5 v: KBC Version 08.50.00 serial: N/A
           UEFI [Legacy]: HP v: Q81 Ver. 01.08.00 date: 07/16/2019
CPU: Quad core AMD Ryzen 3 PRO 2300U w/ Radeon Vega Mobile Gfx (-MCP-) cache: 2048 KB
           clock speeds: max: 2000 MHz 1: 1243 MHz 2: 1229 MHz 3: 1235 MHz 4: 1453 MHz
Graphics: Card: Advanced Micro Devices [AMD/ATI] Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series]
           Display Server: x11 (X.Org 1.20.4 ) drivers: fbdev,ati (unloaded: modesetting,vesa,radeon,amdgpu)
           Resolution: 1920x1080@77.00hz
           OpenGL: renderer: llvmpipe (LLVM 9.0, 128 bits) version: 3.3 Mesa 19.2.0-devel