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While it's true that 401k is not presented as an Account Type option in the scenerio described by the user, that apparent problem can be easily overcome.
The user should select "Brokerage" as the account type.
When the setup/download is finished, the user will then have a new, connected Brokerage account in Quicken.
The user should open the Edit Account Details dialog for that new Brokerage account, then click the radio button to make the account "Tax deferred". At that point, the "Convert to 401k/IRA/529" button will appear and clicking that button will allow the user to convert the account to a Quicken 401k account.
[When creating a new connected "Complete Investing" 401k account (in Q2020 R30.10), there is also no option to select 401k for the account type when Quicken displays the account(s) discovered. But in this case, choosing "Brokerage" results in a new 401k account.] [The second problem noted by the user {"all individual shares turn to cash (1 share becomes $1)} has been noted by others in the Community, and I see it also in my test. I did not attempt to address that second problem; but my guess is that switching to "Complete Investing" would eliminate the problem. And in a "Complete Investing" account, the user can simulate the simplicity of the "Simple Investing" environment by manually entering only Quicken "Adjust Share Balance" transactions (one for each security in the account) each time an account statement is issued.]