Umbrella issue for 26.0 testing. Please help testing on a wide variety of supported platforms, as well as interaction with different software.

Let us know which version you tested on which operating system.

If you find an issue, please search Github for known issues first and then open a new Github issue.

*This meta issue should not be used to report bugs, as a single thread makes it impossible to track more than one topic.*

See [26.0 Draft Release Notes](https://github.com/bitcoin-core/bitcoin-devwiki/wiki/26.0-Release-Notes-Draft) for a list of changes.

See here for the testing guide: https://github.com/bitcoin-core/bitcoin-devwiki/wiki/26.0-Release-Candidate-Testing-Guide.
{
        if (IsFreeListUsable(bytes, alignment)) {
            const std::size_t num_alignments = NumElemAlignBytes(bytes);
            if (nullptr != m_free_lists[num_alignments]) {
                // we've already got data in the pool's freelist, unlink one element and return the pointer
                // to the unlinked memory. Since FreeList is trivially destructible we can just treat it as
                // uninitialized memory.
                return std::exchange(m_free_lists[num_alignments], m_free_lists[num_alignments]->m_next);
            }
            // freelist is empty: get one allocation from allocated chunk memory.
            const std::ptrdiff_t round_bytes = static_cast<std::ptrdiff_t>(num_alignments * ELEM_ALIGN_BYTES);
            if (round_bytes > m_available_memory_end - m_available_memory_it) {
                
                AllocateChunk();
            }
            // Make sure we use the right amount of bytes for that freelist (might be rounded up),
            return std::exchange(m_available_memory_it, m_available_memory_it + round_bytes);
        }
        // Can't use the pool => use operator new()
        return ::operator new (bytes, std::align_val_t{alignment});
    }
    /**
     * Returns a block to the freelists, or deletes the block when it did not come from the chunks.
     */
    void Deallocate(void* p, std::size_t bytes, std::size_t alignment) noexcept