NVIDIA have a Beta driver available, and this compiles OK with kernel 5.5.   Available from link here:  https://developer.nvidia.com/vulkan-driver

I have installed this and – interestingly – it still gives a ‘tombstone’ at # startx, but appears to run OK despite that ?:

[60044.039448] ------------[ cut here ]------------
[60044.043355] refcount_t: underflow; use-after-free.
[60044.047445] WARNING: CPU: 1 PID: 45401 at lib/refcount.c:28 refcount_warn_saturate+0xa6/0xf0
[60044.055201] Modules linked in: nvidia_drm(PO) nvidia_modeset(PO) nvidia(PO) drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm rfcomm cmac bnep btusb btrtl btbcm btintel bluetooth ecdh_generic ecc hid_logitech_hidpp joydev hid_logitech_dj vmnet(O) vmw_vsock_vmci_transport vsock vmw_vmci vmmon(O) sunrpc vfat fat snd_hda_codec_hdmi x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass iTCO_wdt iTCO_vendor_support snd_hda_codec_realtek snd_hda_codec_generic ledtrig_audio crct10dif_pclmul crc32_pclmul snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_hda_core snd_hwdep snd_seq hp_wmi ghash_clmulni_intel snd_seq_device sparse_keymap intel_cstate intel_uncore rfkill snd_pcm intel_rapl_perf pcspkr wmi_bmof snd_timer snd soundcore i2c_i801 lpc_ich binfmt_misc crc32c_intel e1000e wmi fuse [last unloaded: syscopyarea]
[60044.130834] CPU: 1 PID: 45401 Comm: Xorg.wrap Tainted: P O 5.5.0 #1
[60044.137883] Hardware name: Hewlett-Packard HP Z220 CMT Workstation/1790, BIOS K51 v01.87 06/10/2019
[60044.146405] RIP: 0010:refcount_warn_saturate+0xa6/0xf0
[60044.151022] Code: 05 95 70 cf 00 01 e8 57 02 d1 ff 0f 0b c3 80 3d 83 70 cf 00 00 75 95 48 c7 c7 e0 ac db a5 c6 05 73 70 cf 00 01 e8 38 02 d1 ff <0f> 0b c3 80 3d 62 70 cf 00 00 0f 85 72 ff ff ff 48 c7 c7 38 ad db
[60044.169341] RSP: 0018:ffffa1f443d93da0 EFLAGS: 00010286
[60044.174167] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[60044.180902] RDX: ffff9460cdc5d300 RSI: ffff9460cdc58748 RDI: ffff9460cdc58748
[60044.187663] RBP: ffff9460c934bce8 R08: 0000000000000000 R09: 0000000000000422
[60044.194432] R10: 0000000000aaaaaa R11: 0000000000000000 R12: ffff9460342a3ae8
[60044.201205] R13: ffff9460342a3800 R14: 0000000000000008 R15: 0000000000000000
[60044.208005] FS: 00007f86743bb740(0000) GS:ffff9460cdc40000(0000) knlGS:0000000000000000
[60044.215760] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[60044.221200] CR2: 00007f867440fe20 CR3: 0000000378434006 CR4: 00000000001606e0
[60044.228021] Call Trace:
[60044.230167] nv_drm_atomic_helper_disable_all+0xe7/0x280 [nvidia_drm]
[60044.236328] nv_drm_master_drop+0x1d/0x60 [nvidia_drm]
[60044.241190] drm_drop_master+0x19/0x30 [drm]
[60044.245190] drm_master_release+0x8c/0xb0 [drm]
[60044.249455] drm_file_free.part.0+0x24a/0x2c0 [drm]
[60044.254062] drm_release+0x46/0x80 [drm]
[60044.257717] __fput+0xbc/0x250
[60044.260497] task_work_run+0x84/0xa0
[60044.263796] exit_to_usermode_loop+0x95/0xa0
[60044.267778] do_syscall_64+0x1bc/0x210
[60044.271247] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[60044.276028] RIP: 0033:0x7f867459a8e7
[60044.279303] Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 41 c3 48 83 ec 18 89 7c 24 0c e8 e3 fb ff ff
[60044.297836] RSP: 002b:00007ffd1525edc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[60044.305193] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 00007f867459a8e7
[60044.312132] RDX: 00007ffd1525ede0 RSI: 00000000c04064a0 RDI: 0000000000000003
[60044.319053] RBP: 00007ffd1525eec0 R08: 0000000000000000 R09: 00007ffd1525ec50
[60044.325968] R10: 00005613dbd74731 R11: 0000000000000246 R12: 0000000000000003
[60044.332858] R13: 0000000000000001 R14: 0000000000000000 R15: 00007ffd1525ede0
[60044.339796] ---[ end trace c50979c45ab47e72 ]---

This is – of course – Beta-quality code, so use at your own risk!

Robert Gadsdon.   January 27th 2020