The global chip shortage is mostly for older planar nodes, but few companies are willing to invest in building new 40nm or 28nm fabs, and it is hard to increase production in the old fabs when they are already running at 100% capacity. At a time when the production capacity for older nodes is fixed, there has been a large increase in demand for electronics products due to the pandemic. Now every electronics device maker has over-ordered in an attempt to secure enough parts to keep their own production going, so the chip design companies have placed huge orders with the fabs, which can’t keep up with the demand. Another factor is that the chip design companies and the chip fabs are raising prices and demanding upfront payments for future production.
The Librem 5 has been hit particularly hard, because NXP caters to the automotive industry, which has suffered worse parts shortages than most other industries, because they tend to use the older planar nodes and they need parts with long-term support. NXP promises 15 years of production for the i.MX 8M series, so Purism is competing for parts with big automotive companies, which are NXP’s bread and butter. It is not like Purism can call up NXP and convince them to send them a rush batch of the i.MX 8M Quad, when NXP has Ford and VW screaming at them for parts.
Purism can use a different kind of RAM and maybe change other parts like the sensors, but I don’t think that there is much that Purism can do about the i.MX 8M Quad processor, except place its orders and wait. Occasionally, the electronics suppliers get their hands on small amounts of the i.MX 8M Quad and sell them at inflated prices, so Purism can snatch those up when they appear for sale, but the amounts are so small, that I don’t think it helps with the L5, but maybe it helps with the L5USA.
The other possibility is to completely redesign the L5 to use another chip, but all the available options (RK3399, RK3566, i.MX 8M Plus, S922X) have drawbacks in terms of Linux support or power consumption, and it would probably take longer to redesign the L5 than simply wait for the i.MX 8M Quad.