I apologize that you probably know nearly all I am going to mention, but, to be thorough.
Something like this question gets asked - often.
Personally, I think the first questions would be - What is your Personal Threat Model. But you have probably already answered that to yourself.
https://forum.qubes-os.org/t/personal-threat-model/16402
Is it a requirement of yours that the laptop have anti-tamper verification? I guess not, as I don’t know of a 17 inch that has that.
More recently a question similar to yours:
It is possible, with some laptops to attach an external screen, thereby much larger than 17 inches.
I have owned two different 17 inch laptops, and one must still tweak - increase the size of the characters on the screen. 17 inch laptops can become burdensome to carry around.
As a quick view for how a modified screen might look, Another live version of Linux offers an alternative (well, just in font size) Easy-OS. EasyOS Kirkstone-series version 5.3.1. Requires one download and install it to a USB boot it up. I start this on a Lenovo X-230 with a 12.5 inch screen. and it is easy on my old eyes.
Perhaps someone create a version of Qubes that resembles this kind of character size, and screen visibility. I guess someone could read that screen much further away.
If you are thinking that it would be better to buy a used laptop and install Qubes yourself. There are different quality screens. Someone suggested to me Lenovo T480, as it is an Eighth generation processor, and some models can accommodate a lot of memory. Beware, I read some T480’s have memory soldered in, which makes upgrades, I guess difficult or impossible. There are several different pieces of hardware in T480. I have not owned one. And as of now, one can not install a measured boot, to verify if it has been tampered with. I think there is an ‘anti-evil maid’ possible.
You did not say if you were in the US or Europe - or --In the US the manufacturers which are well known are Insurgo, and for brand new machines, Purism Librem. In Europe there is NitroKey, NovaCustom.
and of course there is the compatibility list; HCL Hardware compatibility list (HCL) | Qubes OS
Which has this –
Cheers.