Yes, this basically works as described in the original question using the Subscriptions module. You can simply add subscription an non-subscription products to a Sale Order. Those with the subscription flag will be re-invoiced by your subscription plan.
You can refer to the documentation on this topic here: https://www.odoo.com/documentation/18.0/applications/sales/subscriptions.html
A summary of the configuration an behavior is visualized in the tutorials as well: https://www.odoo.com/slides/20
Now, I don't remember by heart whether the 'first service will be invoiced at the end of the installation' part is described in there as well. If it isn't: 'end of installation' isn't really something Odoo would know without you telling it. To have this work, you would want to define your 'first service' product to have an Invoicing Policy other than Prepaid/Fixed Price so you can either track the completion of the initial setup using a Milestone or set the 'Delivered Quantity' manually (next to other options).
Can this get some attention? I am curious how this is supposed to work out. I have hardware and a subscription in a quote, somehow the one time charges are recurring even though they are not enabled as subscriptions. This seems illogical for how frequent this use care would come up in the wild.
Unfortunatly, not for me.
In the last online version, when I add a product with the "subscription" box ticked + a product WITHOUT the subscription in the SAME QUOTE (sales) it show me in the total the recurring total and the oneshot total... nice.
...But, when I set the quote as accepted, it create a monthly invoice with the TOTAL of the quote (and not the subscription product only).
I cannot manage this... I've to create 2 quotes, one for the 1shot and another one for the subcription...
How can I solve this?
Thks!